Bug 1814798 - pt 2. Add a PHCManager component to control PHC r=glandium,emilio

This change adds the PHCManager class which observes a pref to control PHC.
The pref can be changed at runtime and will affect the parent and content
processes.

Differential Revision: https://phabricator.services.mozilla.com/D178754

memory/replace/phc/PHC.cpp

@@ -324,7 +324,7 @@ static const size_t kAllPagesSize = kNumAllPages * kPageSize;
 static const size_t kAllPagesJemallocSize = kAllPagesSize - kPageSize;
 
 // The default state for PHC.  Either Enabled or OnlyFree.
-#define DEFAULT_STATE mozilla::phc::Enabled
+#define DEFAULT_STATE mozilla::phc::OnlyFree
 
 // The junk value used to fill new allocation in debug builds. It's same value
 // as the one used by mozjemalloc. PHC applies it unconditionally in debug
@@ -1399,8 +1399,6 @@ MOZ_ALWAYS_INLINE static void* PageRealloc(const Maybe<arena_id_t>& aArenaId,
     return nullptr;
   }
 
-  MOZ_ASSERT(aNewSize > kPageSize);
-
   Delay reuseDelay = ReuseDelay(lock);
 
   // Copy the usable size rather than the requested size, because the user

memory/replace/phc/test/gtest/TestPHC.cpp

@@ -49,6 +49,8 @@ static const size_t kPageSize = 4096;
 
 TEST(PHC, TestPHCAllocations)
 {
+  ReplaceMalloc::SetPHCState(phc::PHCState::Enabled);
+
   // First, check that allocations of various sizes all get put at the end of
   // their page as expected. Also, check their sizes are as expected.
 
@@ -259,6 +261,8 @@ static void TestFreedAllocation(uint8_t* aPtr, size_t aSize) {
 
 TEST(PHC, TestPHCInfo)
 {
+  ReplaceMalloc::SetPHCState(phc::PHCState::Enabled);
+
   int stackVar;
   phc::AddrInfo phcInfo;
 
@@ -289,8 +293,10 @@ TEST(PHC, TestPHCInfo)
   // possible to reliably get ahold of such a page.
 }
 
-TEST(PHC, TestPHCDisabling)
+TEST(PHC, TestPHCDisablingThread)
 {
+  ReplaceMalloc::SetPHCState(phc::PHCState::Enabled);
+
   uint8_t* p = GetPHCAllocation(32);
   uint8_t* q = GetPHCAllocation(32);
   if (!p || !q) {
@@ -329,6 +335,49 @@ TEST(PHC, TestPHCDisabling)
   free(s);
 }
 
+TEST(PHC, TestPHCDisablingGlobal)
+{
+  ReplaceMalloc::SetPHCState(phc::PHCState::Enabled);
+
+  uint8_t* p1 = GetPHCAllocation(32);
+  uint8_t* p2 = GetPHCAllocation(32);
+  uint8_t* q = GetPHCAllocation(32);
+  if (!p1 || !p2 || !q) {
+    MOZ_CRASH("failed to get a PHC allocation");
+  }
+
+  ReplaceMalloc::SetPHCState(phc::PHCState::OnlyFree);
+
+  // Test realloc() on a PHC allocation while PHC is disabled on the thread.
+  uint8_t* p3 = (uint8_t*)realloc(p1, 128);
+  // The small realloc is evicted from PHC because in "OnlyFree" state PHC
+  // tries to reduce its memory impact.
+  ASSERT_TRUE(p3 != p1);
+  ASSERT_FALSE(ReplaceMalloc::IsPHCAllocation(p3, nullptr));
+  free(p3);
+  uint8_t* p4 = (uint8_t*)realloc(p2, 8192);
+  // The big realloc is not in-place, and the result is not a PHC
+  // allocation, regardless of PHC's state.
+  ASSERT_TRUE(p4 != p2);
+  ASSERT_FALSE(ReplaceMalloc::IsPHCAllocation(p4, nullptr));
+  free(p4);
+
+  // Test free() on a PHC allocation while PHC is disabled on the thread.
+  free(q);
+
+  // These must not be PHC allocations.
+  uint8_t* r = GetPHCAllocation(32);  // This will fail.
+  ASSERT_FALSE(!!r);
+
+  ReplaceMalloc::SetPHCState(phc::PHCState::Enabled);
+
+  // If it really was reenabled we should be able to get PHC allocations
+  // again.
+  uint8_t* s = GetPHCAllocation(32);  // This should succeed.
+  ASSERT_TRUE(!!s);
+  free(s);
+}
+
 // This test is disabled for now, see Bug 1845017 and Bug 1845655.
 // TEST(PHC, TestPHCExhaustion)
 // {

modules/libpref/init/StaticPrefList.yaml

@@ -10959,6 +10959,19 @@
     mirror: always
 #endif
 
+#---------------------------------------------------------------------------
+# Prefs starting with "memory."
+#---------------------------------------------------------------------------
+
+- name: memory.phc.enabled
+  type: bool
+#if defined(MOZ_PHC)
+  value: true
+#else
+  value: false
+#endif
+  mirror: always
+
 #---------------------------------------------------------------------------
 # Prefs starting with "midi."
 #---------------------------------------------------------------------------

modules/libpref/moz.build

@@ -62,6 +62,7 @@ pref_groups = [
     "layout",
     "mathml",
     "media",
+    "memory",
     "midi",
     "mousewheel",
     "mozilla",
@@ -172,3 +173,6 @@ else:
     FINAL_TARGET_PP_FILES += [
         "greprefs.js",
     ]
+
+if CONFIG["MOZ_PHC"]:
+    DEFINES["MOZ_PHC"] = True

toolkit/crashreporter/test/CrashTestUtils.sys.mjs

@@ -7,6 +7,7 @@ export var CrashTestUtils = {
   dumpHasStream: null,
   dumpHasInstructionPointerMemory: null,
   dumpWin64CFITestSymbols: null,
+  enablePHC: null,
 
   // Constants for crash()
   // Keep these in sync with nsTestCrasher.cpp!
@@ -61,6 +62,11 @@ CrashTestUtils.saveAppMemory = lib.declare(
   ctypes.default_abi,
   ctypes.uint64_t
 );
+CrashTestUtils.enablePHC = lib.declare(
+  "EnablePHC",
+  ctypes.default_abi,
+  ctypes.void_t
+);
 
 try {
   CrashTestUtils.TryOverrideExceptionHandler = lib.declare(

toolkit/crashreporter/test/nsTestCrasher.cpp

@@ -323,6 +323,12 @@ extern "C" NS_EXPORT void Crash(int16_t how) {
   }
 }
 
+extern "C" NS_EXPORT void EnablePHC() {
+#ifdef MOZ_PHC
+  ReplaceMalloc::SetPHCState(mozilla::phc::PHCState::Enabled);
+#endif
+};
+
 char testData[32];
 
 extern "C" NS_EXPORT uint64_t SaveAppMemory() {

toolkit/crashreporter/test/unit/crasher_subprocess_head.js

@@ -27,3 +27,6 @@ const { CrashTestUtils } = ChromeUtils.importESModule(
 );
 var crashType = CrashTestUtils.CRASH_INVALID_POINTER_DEREF;
 var shouldDelay = false;
+
+// Turn PHC on so that the PHC tests work.
+CrashTestUtils.enablePHC();

xpcom/base/PHCManager.cpp

@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "PHCManager.h"
+
+#include "replace_malloc_bridge.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_memory.h"
+
+namespace mozilla {
+
+using namespace phc;
+
+static const char kPHCPref[] = "memory.phc.enabled";
+
+static PHCState GetPHCStateFromPref() {
+  return StaticPrefs::memory_phc_enabled() ? Enabled : OnlyFree;
+}
+
+static void PrefChangeCallback(const char* aPrefName, void* aNull) {
+  MOZ_ASSERT(0 == strcmp(aPrefName, kPHCPref));
+
+  ReplaceMalloc::SetPHCState(GetPHCStateFromPref());
+}
+
+void InitPHCState() {
+  ReplaceMalloc::SetPHCState(GetPHCStateFromPref());
+
+  Preferences::RegisterCallback(PrefChangeCallback, kPHCPref);
+}
+
+};  // namespace mozilla

xpcom/base/PHCManager.h

@@ -0,0 +1,18 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_PHCManager_h
+#define mozilla_PHCManager_h
+
+namespace mozilla {
+
+// Read the PHC pref and potentially initialise PHC.  Also register a
+// callback for the pref to update PHC as the pref changes.
+void InitPHCState();
+
+};  // namespace mozilla
+
+#endif  // mozilla_PHCManager_h

xpcom/base/moz.build

@@ -257,3 +257,15 @@ LOCAL_INCLUDES += [
 
 if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
     CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
+
+if CONFIG["MOZ_PHC"]:
+    EXPORTS.mozilla += [
+        "PHCManager.h",
+    ]
+
+    DEFINES["MOZ_PHC"] = 1
+
+    UNIFIED_SOURCES += ["PHCManager.cpp"]
+
+with Files("PHCManager.*"):
+    BUG_COMPONENT = ("Core", "Memory Allocator")

xpcom/build/XPCOMInit.cpp

@@ -89,6 +89,9 @@
 #include "mozilla/AvailableMemoryTracker.h"
 #include "mozilla/ClearOnShutdown.h"
 #include "mozilla/CountingAllocatorBase.h"
+#ifdef MOZ_PHC
+#  include "mozilla/PHCManager.h"
+#endif
 #include "mozilla/UniquePtr.h"
 #include "mozilla/ServoStyleConsts.h"
 
@@ -448,6 +451,12 @@ NS_InitXPCOM(nsIServiceManager** aResult, nsIFile* aBinDirectory,
     NS_ADDREF(*aResult = nsComponentManagerImpl::gComponentManager);
   }
 
+#ifdef MOZ_PHC
+  // This is the earliest possible moment we can start PHC while still being
+  // able to read prefs.
+  mozilla::InitPHCState();
+#endif
+
   // After autoreg, but before we actually instantiate any components,
   // add any services listed in the "xpcom-directory-providers" category
   // to the directory service.

xpcom/build/moz.build

@@ -103,3 +103,6 @@ if CONFIG["MOZ_VPX"]:
     LOCAL_INCLUDES += [
         "/media/libvpx",
     ]
+
+if CONFIG["MOZ_PHC"]:
+    DEFINES["MOZ_PHC"] = 1